One of the most confusing aspects related to killswitches is if they're normally open or closed. These two terms seem to be always flopping around as to which is which. You'll find the topic on a forum say one thing, and another post say another. Are you thinking about adding a kill-switch to your guitar anytime soon? We're gonna clear things up for you on how to install each one. At the very least, it's some useful information for those who do their own guitar wiring.
The more common types of killswitches you'll encounter are NO (Normally Open), and NC (Normally Closed). At first glance it would appear that the only correct option to use would be a NC switch right? After all, you wouldn't want an open in your signal! The misconception is that NO switches will work backwards and your guitar will only be heard while the button is pushed.
Actually BOTH normally closed & normally open switches accomplish the same staccato effect we're looking for. The only difference is in the way that each one is wired up. Beware that wiring your switch incorrectly, will in fact give you the opposite effect that killswitches are known for. Lets take a look at each type to get a better perspective.
A normally closed (NC) switch is installed in SERIES & works by creating a gap in your signal path when pressed. In electronic terms, this type of switch creates its opposite, which is an "open". You can think of this like a drawbridge that lets traffic through at all times, but when a ship approaches (or the button is pressed), the bridge folds up & traffic stops flowing through. It's only until the ship passes (or the button is released) that the normal flow continues.
A normally open (NO) switch on the other hand, is installed in PARALLEL & works by grounding out your pickup's signal as soon as it's pressed. Again in electrical terms, this type of switch creates its opposite, which is a "short". The rule with electricity, is that it follows the path of least resistance. In a guitar, the signal starts at the jack & also ends at the jack after traveling through the potentiometers, pickups, and other electrical components. By creating a short at the jack, you essentially make a jumper. This jumper allows the signal to exit as soon as it enters, it creates a shortcut whereas the signal doesn't even reach the pickups. In the end, electricity would rather take the easy way out than have to go through all those pickup windings, resistors, and capacitors.
So to give you a visual representation, here's what a NC switch looks like when it's installed correctly (in series). As soon as you press the button, the little draw bridge opens & signal is interrupted.
Below is how a NO switch looks like after being installed in parallel. Notice that when the button is in its resting position, the signal flows as usual. When the button is pressed however, the signal takes the shortest path back home & ignores the pickups.
BEWARE: Wiring a NC in parallel or a NO in series, will result in your killswitches working in reverse! That means the only time you guitar will make a sound is when the button is pressed. Don't worry if this happens right off the bat, perhaps a simple wire swap will fix the issue.
I hope that dispels the myths about NO vs NC, If you're about to install one of our killswitches, note that they're all normally open (NO) so please wire them in accordingly.
Once you get your kill-switch wired, you'll be set to enjoy a whole new aspect to your playing. Crank that amp & let your fingers soar, don't forget to unleash a barrage of staccato "machine-gun" effects here and there! It's real fun to integrate into your everyday playing & opens the door to new creative possibilities.